Thesis Defence: Investigating metabolic responses to refeeding following a short-term fast with or without daily exercise
November 19 at 10:00 am - 2:00 pm
Victoria (Tori) Bouck, supervised by Dr. Jonathan Little, will defend their thesis titled “Investigating metabolic responses to refeeding following a short-term fast with or without daily exercise” in partial fulfillment of the requirements for the degree of Master of Science in Health and Exercise Sciences.
An abstract for Victoria (Tori) Bouck’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.
Abstract
Introduction: Short-term fasting (48-72 hours) reduces insulin sensitivity and glucose tolerance, which is broadly viewed as an adaptive response to spare glucose for the brain. It remains unclear whether aerobic exercise—which is known to have insulin-sensitizing effects—can attenuate decrements in glucose homeostasis induced by prolonged fasting.
Methods: In a randomized crossover design, 16 healthy adults (8 males/8 females; 24±4 years) fasted for 48 hours with and without the addition of daily exercise (50 minutes cycling @ 60% heart rate reserve (HRR) + 5×1-minute @ 90% HRR with 1-minute rest) performed at the beginning of and 24 hours into the fast. We assessed glycemic responses to a mixed meal tolerance test (MMTT) before and after the 48-hour fast, as well as 24 hours following the reintroduction of normal eating. Between-condition differences in glycemic regulation over 72 hours following the reintroduction of normal eating were assessed via continuous glucose monitoring (CGM).
Results: Fasting alone (FAST) and combined fasting and exercise (FAST+EX) elicited reductions in body mass, capillary and plasma glucose, and plasma insulin and an increase in β-hydroxybutyrate (BHB; all P<0.001), with the FAST+EX condition exhibiting a greater (P=0.02) and more rapid (p<0.01) reduction in capillary glucose, and slightly higher BHB levels at 48 h (P=0.01). Capillary glucose and CGM incremental area under the curve (iAUC) during a 2-hr MMTT were increased ~3-4-fold from baseline at 48 hours fasted (P<0.001), which was unaffected by the addition of exercise (Condition x Time interaction; P>0.3). The 2-hr CGM iAUC was significantly reduced 24 hours following the reintroduction of normal eating compared to 48 hours fasted (with or without exercise, P<0.001), although remained marginally elevated relative to baseline (P=0.01). Glycemic regulation was significantly impaired in the first 24 hours following the fast relative to the subsequent two 24-hour periods, with no differences between FAST and FAST+EX (Condition x Time interaction; P>0.1).
Conclusion: Our results suggest exercise does not attenuate fasting-induced perturbations in glucose homeostasis, and that glucose intolerance is largely—although potentially not completely—reversed 24 hours following the reintroduction of normal eating.
